fix: canonical DELETE scanner + key-only single-index delete (W1) - #371
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September 3, 2026 20:18
… flush rewrite) Stap-0 profiling showed batch DELETE (ExecuteBatchSQL wraps every batch in a storage transaction) was NOT using the tombstone path: the rollback-safe deferral only counted _pendingLogicalDeletes, so db.Flush() still ran the #366 full-file CompactPendingDeletes rewrite (~0.5-0.7s; DELETE stuck at ~12-16K ops/s). - IStorage.BufferTombstoneForCommit (default no-op) + Storage implementation: buffered offsets per file, applied as in-place negative-prefix markers by ApplyBufferedTombstones() inside FlushBufferedAppendsAndOverwrites() (the commit path) AFTER buffered appends are on disk; rollback discards the buffer via ClearBufferedAppends(). - DeleteRecordsCore + the contiguous FW bulk path now buffer the deleted offsets when IsInTransaction instead of incrementing _pendingLogicalDeletes, so the flush-time full-file rewrite is off the batch-DELETE path entirely. - Regression: batch DELETE survives reopen even WITHOUT an explicit Flush after ExecuteBatchSQL (commit already tombstoned the rows). Measured (same machine, Release, comparative harness DELETE 10K of ~100K rows): SQL 0.82s/12K -> 0.24s/41K ops/s, Direct 0.63s/16K -> 0.17s/58K ops/s; --pk legacy 0.16s/62K, fixed-width 0.13s/78K ops/s. Full suite EXIT=0.
- IStorage.TombstoneRecords (default loops TombstoneRecord); Storage batches the in-place negative-prefix markers over one cached read handle and evicts each affected page-cache page once instead of once per row. - ApplyBufferedTombstones (commit path) and Table.TombstoneDeletedPositions (direct non-transactional deletes) route through the batch API; offsets that are not physical records (EOF/already-marked) are skipped safely.
…parse (B3) - TryParseDeleteForBatch now also returns the canonical WHERE column + raw literal; ExecuteBatchSQL groups (where, column, literal) instead of plain WHERE strings. - Table.DeleteMultipleKeys mirrors DeleteMultiple (contiguous-FW gate -> PK fast path -> hash fast path -> generic fallback) but resolves keys directly from the pre-parsed column/literal; the 'col = literal' string and the second TryParseSimpleWhereClause pass are built only when a generic fallback actually runs. - Non-canonical statements keep the string path (mixed tables rebuild on the rare path).
…index columns The structured batch DELETE path (DeleteMultipleKeys) now decodes a minimal row: BuildDeleteKeyColumns computes the needed columns (PK + every loaded hash-index column), and DeserializeDeleteKeyRow walks the legacy variable-length record skipping the unneeded columns' payload parsing entirely, building a 1-3 entry dictionary instead of a full row. DeleteRecordsCore performs the identical PK/hash lookups on that subset. Fixed-width layouts and corrupt rows fall back to the full DeserializeRowFromSpan. Measured (Release, comparative harness DELETE 10K of ~100K rows, median of 3): SQL ~39-42K and Direct ~57K ops/s — neutral within run noise on this small-row workload; the win shows on wider rows / long unindexed TEXT payloads where payload parsing and boxing are skipped. Full suite + 4 CI-filter suites EXIT=0.
D2 profiling (env-gated phase timers) showed TryScanCanonicalDml's DELETE branch never consumed the whitespace/WHERE keyword after the table name, so every canonical 'DELETE ... WHERE col = literal' fell back to the regex path - DeleteMultipleKeys/B1 were dead code in the benchmark harness. - Fix scanner: DELETE now consumes whitespace + WHERE + whitespace before the WHERE column; canonical batch deletes route through the structured DeleteMultipleKeys path. - Diagnostics: Database.CanonicalDeleteStatementsParsed counter + CanonicalBatchDelete_EngagesStructuredPath regression test. - W1: in DeleteMultipleKeys, when the table has no PK tree and exactly one registered hash index (no B-tree manager) whose key is the condition value, delete positions are recorded with the known key - no per-row engine.Read/decode. Profile attribution (DELETE 10K, docs): read+decode 62-82ms, commit markers ~50ms, core 23-56ms, index 5-10ms. Per-row read remains while the delete core must remove each auto-rowid PK entry - next lever is batch PK stale/lazy-rebuild. docs/performance/EXECUTION_PLAN_UPDATE_DELETE.md: combined execution plan + D2 findings.
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Stack
perf/keyonly-delete(PR perf: key-only DELETE row decode (B1) #370) ← perf: batch tombstone writes (C4) + structured batch DELETE (B3) #369 ← perf: apply DELETE tombstones at COMMIT for transactional deletes (no flush rewrite) #368 ← perf: durable Columnar DELETE in-place via tombstone markers (no flush rewrite) #367 ← master.Inhoud
TryScanCanonicalDml's DELETE-tak consumente nooit de whitespace/hetWHERE-keyword na de tabelnaam → elke canoniekeDELETE ... WHERE col = literalviel terug op de regex-path. Gevolg:DeleteMultipleKeys+ B1 (perf: key-only DELETE row decode (B1) #370) waren dead code in de benchmark-harness (verklaart waarom perf: batch tombstone writes (C4) + structured batch DELETE (B3) #369/perf: key-only DELETE row decode (B1) #370 neutraal leken). Nu routeren canonieke batch-deletes door de structured path.Database.CanonicalDeleteStatementsParsed+ regressietestCanonicalBatchDelete_EngagesStructuredPath.DeleteMultipleKeys, wanneer de tabel geen PK-tree heeft en exact één geregistreerde hash-index (geen B-tree manager) waarvan de key de conditiewaarde is, worden posities met de bekende key verwijderd — géén per-rijengine.Read/decode.D2-attributie (env-gated fase-timers, DELETE 10K docs-tabel)
Grote vervolg-hefboom met deze cijfers: de per-rij read + per-rij
Index.Delete(auto-rowid-PK) vervangen door één batch PK stale/lazy-rebuild na een grote delete-batch.Validatie
SharpCoreDB.Tests(Debug) + Release/CI-filter op alle vier de suites: EXIT=0.